Bacteria in lungs protect against asthma

21 May 2014

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Whether or not people develop asthma may be determined in the
first few weeks after birth according to a study of mice funded by
the Swiss National Science Foundation (SNSF). The study suggests
that microbes in the lungs stimulate the newborn's immune system.

Our lungs were long considered to be germfree and sterile. It was
only recently discovered that, like our intestines and skin, our
respiratory organs are colonised by bacteria. Now, tests conducted
on mice by researchers at the University Hospital in Lausanne have
shown that these lung microbes offer protection against allergic
asthma.

The researchers exposed the mice to an extract obtained from
house dust mites. Neonates had a much stronger allergic reaction to
the extract than older mice. This is because the lungs in newborn
mice have not yet been colonised by the microbes that alter the
immune system and make its responses less prone to allergic
reactions.

The researchers have discovered that the process of colonisation
and adaptation takes place during the first two weeks of the mouse's
life. Young mice that were kept completely germ-free remained
susceptible to asthma and had excessive immune responses to dust
mite allergens even later in life. The research was published in
Nature Medicine online [1].

Benjamin Marsland and his team at the University have already
started studying whether lung microbes ensure healthy airways in
humans as well. Pilot studies involving newborn babies in
Switzerland and New Zealand indicate that the situation may be
similar for men and mice. Further studies are required, however, to
identify the potential mechanisms in humans.

Focus on newborns

"There would appear to be a developmental window early in life
that determines whether or not an individual will develop asthma
later," Marsland says. Until now, scientists and doctors have
focused on asthma essentially from the point of view of the course
of the disease and possible direct triggers. "We should probably
focus on a much earlier stage, that of newborns."

What Marsland wants to know now is how big the developmental
window is for building up the immune system in childhood. He hopes
that the new discovery will help prevent asthma. Perhaps by
encouraging pregnant women to eat more fruit and vegetables —
recently Marsland showed that the dietary fibre contained in these
foodstuffs also protects against allergic asthma by altering the
microbial flora. That protection might be passed on to newborn
babies.